Bumping up hadoop-yarn-server-router module to 3.0.0-alpha4 post rebase.

(cherry picked from commit bd9c7b1bec3293fe338553c0d5c3612e6176fb26)
(cherry picked from commit f317e0cb48c16e072aa259a0a7ed71a05274bb80)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-router/pom.xml

@@ -19,12 +19,12 @@
   <parent>
     <artifactId>hadoop-yarn-server</artifactId>
     <groupId>org.apache.hadoop</groupId>
-    <version>3.0.0-alpha3-SNAPSHOT</version>
+    <version>3.0.0-alpha4-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <groupId>org.apache.hadoop</groupId>
   <artifactId>hadoop-yarn-server-router</artifactId>
-  <version>3.0.0-alpha3-SNAPSHOT</version>
+  <version>3.0.0-alpha4-SNAPSHOT</version>
   <name>Apache Hadoop YARN Router</name>
 
   <properties>